The present invention relates generally to machine wear detection, and more particularly, but not exclusively, to component-specific wear determination by analysis of a lubricating fluid.
Machines perform a variety of valuable functions in industry, but they require ongoing maintenance. Because of the costs associated with performing both preventative and corrective maintenance, significant attention is given to developing and implementing efficient maintenance programs. The general goal of most maintenance programs is to protect the machine and prolong its useful life while minimizing down time and other maintenance expenses.
Some maintenance programs are schedule-based. In these, intervals are established for certain preventative maintenance tasks, such as inspection or replacement of certain components or groups of components, and the task is performed upon the expiration of the interval. However, too frequent preventative maintenance is costly, in terms of labor, materials and the loss of use during the needed machine down time. Conversely, increasing the preventative maintenance intervals increases the chance a machine will fail during use, which itself can be costly as well as dangerous and inconvenient. Furthermore, some failures, such as where a component malfunctions due to damage, an inherent defect, improper installation, etc. are often unpredictable and therefore are difficult to head off with preventative maintenance performed solely on a calendar based or use based schedule. Condition-based maintenance programs are attempts to efficiently address these concerns and to reduce the risks of machine failures by determining maintenance, at least in part, based on measurements of the actual condition of the machine.
In a condition-based maintenance program, data is gathered in an effort to ascertain the physical condition of the machine and its various components. This data is then used to guide the scheduling of maintenance, for example by establishing safe limits for a certain measured parameter and then determining the need for maintenance when the measured value exceeds those limits. Since the condition of the machine's fluids can provide information about the condition of the machine, measurements performed on the machine's fluids are a useful source of input data for condition-based maintenance programs. For example, when the moving parts of a machine experience wear, fine particles are typically dispersed into the machine's lubricating fluid. A determination of the amount of these fine particles in the fluid therefore can be used to assess the amount of the machine wear.
However, the simple quantification of fine particles in the lubricating fluid is a non-specific indication of wear. In other words, the fine particles may have originated from various sources, each of which can be experiencing wear. As a result, particle count measurements can fail to capture the true state of the machine, and this potential for error increases as the number of wearing parts increases. For example, a gas turbine engine may have several bearings along a drive shaft. Accordingly, a situation could arise where one of these bearing wears at an abnormally high rate, putting the engine at risk of failure. However, the remaining bearings could wear at sufficiently low rates that the overall quantity of wear material in the lubricating fluid of the bearings does not indicate any impending failure. Unfortunately, the ability to detect such a condition or to otherwise provide component-specific wear information in machines is limited. Accordingly, there is a need for systems and techniques that obtain more specific machine wear information, and in certain forms, the present invention addresses this need. In these or in other forms the present invention provides useful and cost effective improvements for the condition-based maintenance of machines.